Satelli te oceanography, as the term is used in this book, is a generic term that means application of the technology of aerospace electromagnetic remote sensing to the study of the oceans. The key words here are "application of technology ••. to the study of the oceans." The goal is to learn more about our planet's hydrosphere. As such, remote sensing technology is another tool in the oceanographer's sea bag, just like a bathythermograph or a plankton net. But is a whole book necessary if remote sensing is just another tool? While it is true that no one has written a whole book on plankton nets, volumes have been written about what is found in those nets. Today's state-of-the-art measurements from spacecraft or aircraft first must be interpreted in terms of their physics; then the interpretations must be understood in terms of oceanic processes. This is not materially different from the analogy to Ii plankton net; marine biolo­ gists still argue about what didn't get caught in the net.